1. Field of the Invention
The present invention relates to stretching bicycles and more particularly to a portable bicycle having a compact size after disassembly so as to save storage space while being carried.
2. Description of the Prior Art
Conventionally, a stretching bicycle has a separable crossbar consisting of a front bar and a rear bar releasably secured to the front bar by a fastening mechanism. Thus, the maximum length reduction of the bicycle is defined by the front and rear bars, the head tube, and the seat tube.
The present inventor had filed an application in the U.S. patent application Ser. No. 10/346,128 on Jan. 17, 2003 (hereinafter prior art) which is incorporated herein by reference. Prior art discloses a stretching bicycle characterized as follows. Two parallel main seat tube and auxiliary seat tube are extended upwardly from the bottom bracket in a slightly inclined direction. Also, the main seat tube is laterally displaced a predetermined distance from a lengthwise direction of the bicycle (i.e., not aligned with the crossbar). A seat stay is extended rearwardly from both the main seat tube and the auxiliary seat tube to the rear wheel. A seat post is slidably inserted into the main seat tube. A laterally extended bar is interconnected to the seat post and a saddle such that the saddle is adapted to align with the lengthwise direction of the bicycle again (i.e., aligned with the crossbar). The lower portion of the auxiliary seat tube is coupled to a reinforcement tube and a top thereof is coupled to a crossbar having both ends open. Two T-shaped gaps are formed adjacent a front end and a rear end of the crossbar respectively for providing flexibility thereto. A sliding tube has a front end fixedly coupled to a head tube and a rear end adapted to insert through the crossbar. Also, a lengthwise first groove and a lengthwise mated second groove are formed on the crossbar and the sliding tube respectively for facilitating a correct coupling of the crossbar and the sliding tube and preventing both from turning relative to each other. Two quick releases are adapted to clamp around the gaps for securing the sliding tube to the crossbar. Prior art has advantages of being structurally strong and making a maximum length reduction of the bicycle achievable. However, prior art still has the disadvantage of having a relatively heavy frame due to the provision of the main seat tube, the auxiliary seat tube, and the laterally extended bar. Moreover, the saddle and the seat post are not aligned vertically. Hence, the weight of the driver may not totally transmit to other components of the frame via the saddle, the laterally extended bar, and seat post. In other words, the joining portion of the laterally extended bar and the seat post bears a great portion of the weight of the driver. This in turn has the potential of breaking the joining portion while driving. This is dangerous. Thus, it is desirable to provide a portable bicycle having a compact size after disassembly in order to overcome the above drawbacks of the prior art.